#!/bin/bash
shopt -s globstar

for file in ./**; do
  if [[ -f $file ]]; then
    IFS=. read -r -d / -a parts <<< "${file##*/}/"
    for i in "${!parts[@]}"; do
      if [[ ${parts[i]} != *[![:alpha:]]* ]]; then
        parts[i]=${parts[i]:0:1}
      fi
    done
    printf -v newname %s. "${parts[@]}"
    echo mv "$file" "${file%/*}/${newname%.}"
  fi
done